@article{Bird_1973,
    doi = {10.1016/s0022-0000(73)80045-5},
    url = {https://doi.org/10.1016%2Fs0022-0000%2873%2980045-5},
    year = {1973},
    month = {apr},
    publisher = {Elsevier {BV}},
    volume = {7},
    number = {2},
    pages = {218--236},
    author = {Malcolm Bird},
    title = {The equivalence problem for deterministic two-tape automata},
    journal = {Journal of Computer and System Sciences}
}

@article{Bird_1973, doi = {10.1016/s0022-0000(73)80045-5}, url = {https://doi.org/10.1016%2Fs0022-0000%2873%2980045-5}, year = {1973}, month = {apr}, publisher = {Elsevier {BV}}, volume = {7}, number = {2}, pages = {218--236}, author = {Malcolm Bird}, title = {The equivalence problem for deterministic two-tape automata}, journal = {Journal of Computer and System Sciences} }